Rheostat.



PATENTED DEC. 13, 1904. W. -L. SCHMIDT.

RHEOSTAT.

APPLICATION FILED JUNE 7, 1904.

2 SHEETSSHEET 1.

N0 MODEL.

Witt wows I PATENTED DEC. 18, 1904,

W. L. SCHMIDT.

RHEOSTAT.

APPLICATION F'ILED JUNE 7, 1904.

2 SHEETS-SHEET 2 N0 MODEL.

Witneoswo W uorum:

No, 777,439, Patented December 13, 1904.

UNITED STATES PATENT OFFICE.

WILLIAM L. SCHMIDT, OF EASTON, PENNSYLVANIA, ASSIGNOR OF ONE- HALF TO WVILLIAM S. BROTZMAN, OF EAS ON, PENNSYLVANIA.

RHEOSTAT.

SPECIFICATION forming part of Letters Patent No. 777,439, dated December 13, 1904. Application filed June '7, 1904. Serial No. 211,546. (No model.)

T all whom it y oncern: journal-openings 8 and 10, located, respec- Be it known that LVVILLIAM L. SCHMIDT, a ti vely, in the front and rear plates 6 and 7. citiZenoftheUnited States, residingatEaston, Mounted concentrically on the projecting in the county of Northampton and State of end of the shaft 16, which carries the drum 5 Pennsylvania, have invented new and useful 15, is the gear-wheel 18, which is adapted to Improvements in Rheostats, of which the fol engage and mesh with the pinion gear-wheel lowing is a specification. 19, that is mounted for rotation on the pro- 55 This invention relates to an improved form jecting end of the stub-shaft 20, arranged in of rheostat and comprises two cooperating parallelism with the adjacent end of said shaft cylinders or winding-drums, one of which is 16. h [ounted on the stub-shaft 21 is the composed of non-conducting material, while master driving gear-wheel 22, which is adaptthe other is made of conducting material, said ed to engage and mesh with the pinion 19, 6O

drums being moved relatively to each other and which is adapted to be manually operto transfer a known resistance of wire which ated by reason of the handle 23, keyed to the 5 is unwound from one drum in any number of projecting end of said shaft. The outer proturns or convolutions to be simultaneously jecting end of the shaft 17 is likewise prowound or wrapped upon the other to thereby vided with a driven gear 24, that is adapted 5 include or withdraw the same from the cirto engage and mesh with the driving-gear 22.

cuit to be Varied, which introduction or with- It will be observed that by this train of gears drawal of resistance is accomplished without both drums may be simultaneously revolved sparking, and permitting any resistance dein opposite directions by a turn of the opersired between certain minimum and maximum atinghandle in a given direction, and there- 7 limits. by serve to reel or wind the resistance-wire In the accompanying drawings, Figure 1 to be transferred from one to the other, as

5 represents a front elevation of the rheostat. desired. It will also be seen that by such Fig. 2 represents a sectional View thereof. an arrangement of gearing and the relative Like numerals of reference indicate like sizes or ratlos of same by one complete turn parts In both figures. of the operating-handle the drums may be Referring to the drawings by numerals, 5 caused to rotate several times to cause the 3 represents the casing or housing of the rheocomplete transfer of the wire from one to the stat, the general shape of which is rectanguother of said drums according to the direction lar. This casing has front and rear walls or in which said handle is turned. Another adplates 6 and 7. These walls or plates are vantage which is derived from the arrangepreferably made of light castings and are pro- Inent of the gears and the moving parts. in

35 vided with openings 8, 9, and 10 for purposes the manner shown and described is that they to be hereinafter described. The plates are are brought into proper and close relationconnected to each other by rods 11 and 12, ship in front of the machine, where they may 5 which extend in parallelism, as shown. The be inclosed by the front plate 25, which is seside walls 13 of the casing are preferably cured, as shown, by the stud-bolts 26.

4 formed of an enveloping sheet of wire-screen 1 will now proceed to describe the special to provide for ventilation, and thereby allow construction of the respective winding-drums. of the radiation of any heat as soon as it is The drum or cylinder 1A is composed of con- 9 generated by the resistance-coils within the ducting material, such as aluminium-bronze, casing. WVithin the casing thus constructed and is preferably shown as being made up of 45 are arranged winding-drums 14 and 15, that a series of cylindrical castings or disks 27, that are mounted in operative relation to each are rendered rigid by means of the rims or other, respectively, on shafts 16 and 17, flanges 27 and which are mounted on said which latter are mounted for rotation in the shaft 17 in a manner to have a common axis of rotation and which are insulated therefrom and from each other. These disks are pro vided on their peripheral faces with spiral grooves 28, that are left-handed in direction, as shown, and which are adapted to serve as guides for the strands or convolutions of wire to be wound thereon. This constitutes one member of the winding and transferring pair. By constructing the conducting cylinder or drum in sections or disks, as shown, the number of coils of resistance-wires may be multiplied correspondingly, whereby a given resistance may be transferred one way or the other more quickly.

15 represents the opposite cooperating drum or member of the winding pair, which comprises an elongated hollow cylinder of nonconducting material, such as porcelain, the peripheral plane of which coincides with that of the drum 14 and which is grooved spirally in a right-hand ed direction on the said periphery by guiding-grooves 28, that are arranged in operative alinement with the grooves located on the opposite winding-drum.

29 indicates the resistance-wire of the coils wound about the respective drums. This wire to be suitable for such a purpose should be of the highest specific resistance and should be of such material as will change the least with changes of temperature, and this resistancewire may be of elastic braided form or twisted and composed of several small wires. 30 and 31 indicate annular strips which are respectively mounted on the rear end or face of said drum in concentric relation and which constitute the movable contact-terminals of the drum-carried circuit to be presently described. From the contact strip 30 one branch of the said drum-carried circuit leads longitudinally through said drum in a manner to be concealed in one unbroken strand of wire 32, insulated as shown. The branch forming the circuits return to the contact strip or terminal 31. This latter branch is composed of broken lengths 33, threaded through drill-holes 3 1 to form bends, as shown, in a manner to provide a wire reinforce and present a longitudinally-extending series of properly-spaced circuit-loop members, the ends 35 of which project into the plane of the grooved periphery of said drum which is adjacent thereto and which are connected, respectively, with the wire ends of the re-- spective coils of wire 36, which are arranged in a series corresponding to the disks upon which they are normally wound and by reason of the successive electrical connection of said loops with said disks by the cross connectingwires of the respective coils are brought into operative serial connection with each other to complete the return branch of the drum-carried circuit to its terminal or contact strip 31. From this arrangement it will be observed that the smallest fractional part of the resistance material or wire transferred from the one drum to the other changes the current passing through said circuit correspondingly and that the resistance may be introduced and withdrawn without sparking and that by the complete unwinding of every convolution of wire from the said drum 15 and its transference to the drum 14 there is still left a return branch circuit, which is completed by reason of the alternate connections of the loops and the disks through the wire 29 of the coils 36 in succession throughout the entire series to the contact-strip 31.

3:7 and 38 indicate the binding-posts, which serve to form the terminals of the external circuit and their connection with the partial circuit carried by rheostat. Each bindingpost is shown as being adapted to be removably attached to the thimble 39, which extends through the rear plate and which is interiorly threaded and which is provided with a spring 40, which abuts or shoulders at one end against the inner projecting end of said post and with its opposite end against a bearing-button 4:1, projecting inwardly against the adjacent oontact-strip carried by the drum 15.

Having thus described my invention, what 1 claim is 1. In a rheostat the combination of a pair of oppositely-turning winding-drums, one of which is composed of non-conducting material, conductors carried by said drums, which may be transferred from one to the other, suitable connections for including an external circuit, and means for bringing into operative relation with said connections only that portion of the wire conductor that is wound about the non-conducting drum, and that extends beyond the limits of the opposite drum member, substantially as described.

2. In a rheostat, the combination of a pair of oppositely-turning wimling-drums one of which is made of conducting material while the other is made of non-conducting material and which are provided with one or more conductors wound thereon, and which are geared together substantially as described, and suitable cross connections by which said conductors are linked together and put in circuit when wound upon the non-conducting drum, substantially as described.

3. In a rheostat, the combination of a pair of oppositely-turning winding-drums, which are provided with a plurality of conductors wound thereon, and which are geared together to be driven at a rapid peripheral speed, substantially as described, one of said drums bcing made of non-conducting material and provided with peripheral spiral grooves, and carrying a partial circuit made up in one branch thereof by a series of connections, while the other of said drums is made of a series of con- .ducting-disks that are suitably insulated, and

that are provided circumferentially with spiral grooves, and that correspond in number with the ad acent series of connections on the opposite drum, said disks being adapted to receive the transfer of the conductor wound on the adjacent portion of the opposite drum, without separating the cross connecting-wires of said coils with the connections of the partial circuit, whereby the said partial circuit is at all times complete within said rheostat, substantially as described.

4. In a rheostat, the combination of a pair of oppositely-turning Winding-drums, one or more conductors Wound thereon, and geared together substantially as described, one of said drums being made of conducting material while the other is provided circumferentially with a facing of non-conducting material, and which carries a partial circuit, that is completed in one of its branches by cross connections at intervals with the oppositely-arranged conducting-drum, said partial circuits terminating in contacts and binding-posts arranged, respectively, in sliding contact with the drumcarried contacts, substantially as described.

5. In a rheostat, the combination of an inclosing case having ventilative openings, horizontal rotary shafts mounted in parallelism therein, and geared together to be rotated in opposite directions, drums mounted to rotate on the respective shafts, and arranged to present their peripheries in proximity and in a given plane, one of said drums being made of non-conducting material, and provided on its periphery with right-handed spiral grooves, while the other of said drums is made of conducting material and provided circumferentially with left-handed spiral grooves arranged in operative alinement with those of the opposite drum, wire conductors carried by said drums, which may be transferred by winding from one to the other, suitable connections for including an external circuit; and means for cutting in circuit only that portion of the wire conductors that is wound about the nonconducting drum and that extends beyond the limits of the drum member, substantially as described.

In testimony whereof I afiiX my signature in presence of two witnesses.

\VILLIAM L. SCHMIDT.

Vitnesses:

G. M. VVELLER, GEORGE HULL. 

